We cant protect everything

Technical University of Denmark

Why is Denmark particularly exposed to water?

Because we are one of the countries most at risk of flooding in the future. We talk a lot about temperatures in relation to climate change, but what's going to affect us most is the water. We haven't been used to it being a big problem because most of our natural disasters have been wind-related, except perhaps for the cloudburst in 2011, but that will change in the future. And virtually all of Denmark is at risk.

We have 98 municipalities, 75 of them coastal, so they have to decide what to do with their shoreland. That problem needs to be solved, urgently. All coastal towns in Denmark are currently building small dykes according to need, but there is no coherent plan. We need to realise that we cannot protect everything. We cannot build dykes along all of our coastlines, so we need to prioritize what to do with the values that are in danger of being flooded.

And surely, building dykes doesn't come cheap?

No, and in addition to the monetary and resource costs, dyke construction also has major consequences for the surrounding nature and can destroy salt marshes and natural areas such as the Wadden Sea. And the challenge is how high the dyke should be. Do we need it to withstand a 'regular' storm surge, or rather an event that only happens every 150 years? At some point, we will witness an incident that the dyke can't withstand. And when you build dykes, you also create an expectation that the problem is solved, and then you build even more behind the dyke.

We should also bear in mind that there are a lot of CO2 emissions associated with the entire process of building dykes, from recovery of materials to transport. It would be impossible to achieve our climate goals if we were to build dykes around the entire country.

Which areas are particularly at risk?

The vast majority of urban development in Copenhagen over the past 25 years have taken place near the water's edge, and these areas are very vulnerable to severe storm surges. Unfortunately, a lot of cities have copied this trend with many new and planned homes being located close to the water. In some places, such as Copenhagen, dykes should be built sooner rather than later, because the costs will be too high if you don't, while in other places it would be a bad idea.

What are the consequences of doing nothing?

An analysis from Danmarks Nationalbank has pointed out that our economic stability is threatened by rising sea levels. The cost of a storm surge along the entire Baltic Sea coast could reach tens of billions of kroner, and reconstruction could take many years.

Many homes close to the coastline will become worthless in the future, but people haven't realized it yet. They risk betting their entire fortune on something that will be flooded in the foreseeable future. Exclusive homes worth many millions will suddenly lose their value.

How do we solve the problem?

First, we must stop building homes close to the water or on low-lying plots. It's a really bad idea to build in former port areas that will require protection from dykes in the future.

Another effective measure is to build houses that are flood-resistant. This means building houses that are either on stilts or have waterproof membranes installed that prevent water from seeping into the house. It is also necessary to think in terms of nature-based coastal protection solutions. Salt marshes, for example, may move further inland.

How do we decide what to save?

It will be a difficult decision. A purely economic yardstick can be applied, but that is not enough. Based on economic criteria, the small islands in, for example, The South Funen Archipelago are not worth protecting. But social factors also come into play, and nature is often not taken into account when considering things from a purely economic perspective. The solutions should take place supramunicipally, so either the state or the regions take responsibility for implementing them.

How long do we have?

The only thing we can say for sure is that a storm surge will come. In my lifetime, we will experience floods of such a magnitude that the clean-up work will take four or five years, if we are not prepared. In some parts of the world, entire cities have already begun to relocate, such as Jakarta in Indonesia, and we may also have to do that with Copenhagen if we do not focus on the long-term.

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